


The Nightmare Agenda

by LA_Peach



Category: Undertale (Video Game)
Genre: Anal Sex, Enemies to Lovers, Exhibitionism, M/M, Over stimulation, Sanscest - Freeform, Tentacle Sex, berryscary, mud and rain
Language: English
Status: Completed
Published: 2019-11-12
Updated: 2019-11-12
Packaged: 2021-01-29 11:23:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,009
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21409387
Author URL: https://archiveofourown.org/users/LA_Peach/pseuds/LA_Peach
Summary: Nightmare instigates a fight with Blue in the muddy rain in Snowdin, which leads to some other mud-born activities. I'ts like wrestling? But it's not wrestling.
Relationships: Blueberry/Nightmare
Comments: 14
Kudos: 108





	The Nightmare Agenda

**Author's Note:**

> This is a gift to all of my twitter followers, who suggested and voted on the subject, as a thank you for reaching 500. It was a lot of fun, as always, and comes with a nice cover page.
> 
> Edit: Sometimes I forget you guys can't read my mind. So... I don't write the AU's as if they are separate universes, but rather they are different areas, or regions (of the underground or the surface, I bounce around) that happen to share common species (like the skeletons) and silly circumstantial things like usually having a Queen as ruler.

“You take that back, mister!”

“Or what? You’ll ‘nyeh’ me to death? Bring it on, toothpick. I’m sick of looking at you.”

Sans and Dream stood off to one side, watching the other two as they fought. Dream was not particularly impressed with the display of machismo but was too tired of trying to stop Nightmare anymore. The dark skeleton and Blue just seemed to rub each other the wrong way.

Flipping up his hoody against the light drizzle, Sans watched with his usual bored form of interest. “What did Nightmare say this time?”

Dream just shrugged. “An insult, no doubt. Probably aimed at Blue’s paramour.”

Sans just nodded. Nothing could set Blue off quite like insulting the queen he had loved from afar for so long. 

The day was dreary, with heavy clouds rolling slowly overhead, looking about ready to rain on them. Most of Snowdin’s fluffy snow piles had melted away in the unexpected heat, leaving large puddles of mud everywhere. Sans wasn’t too keen on getting mud all over his slippers but tried to act like he didn’t care. It took too much energy anyway. He gazed at the grey sky, sure that soon they would all be drenched to the bones.

“Why do you guys always have to come through here anyway? It’s not exactly the fastest way to our palace from your home.” 

Dream pondered this, putting one thin finger to his delicate chin in a pensive gesture. “You know, Nightmare always insists.”

Blue’s fists shook as he screamed, defending the honour of his Queen. Nightmare just smiled widely, showing lots of pointy teeth. “What’s got you all up in a huff anyway? That queen of yours is nothing but a dusty, dried up old goat.”

“That’s it!” Blue pushed up non-existent sleeves, making fists and holding them out in front of him. He bounced on the balls of his feet in the mud, ready to fight. “You want to do this? Come and get me you… you rude, nasty skeleton!”

Nightmare chuckled, holding his arms and tentacles out wide. “You think you can handle this? I’ll even give you the first…” His mocking tone suddenly ended as Blue socked him in the chin, smears of ectoplasmic black goo flying in all directions. He regarded Blue, who was still bouncing on his feet, with a stunned expression.

“He’s a trained soldier, you idiot!” Dream shouted at them. 

“Fine,” Nightmare wiped a bit of what might pass for blood from his chin. “Now you’re gonna get it.” With an untrained fist, he lashed out at Blue, who cleverly crossed his forearms and blocked it without much issue. There was a seriously glint in his eye, he was ready.

Nightmare unleashed a flurry of blows but none of them could hit home. Blue dodged and blocked them all, occasionally sidestepping and releasing one calculated punch to Nightmare’s face, shoulders, and chest.

The dark skeleton grunted, becoming increasingly agitated, taking every wallop with gritted teeth and trying to find an opening.

A clap of lightening announced the beginning of a hard and heavy rain. Sans and Dream were immediately soaked and miserable. Blue and Nightmare pretended not to notice. Through streams of water running down his face, Sans mumbled, “I’m surprised Nightmare hasn’t used his tentacles… oh. There he goes.”

One slimy, dripping tentacle wiped out, curling around Blue’s leg and tossing him into the air. He landed with a splat, angry. “Hey! N-no tentacles! It’s not fair!” 

“Fairs are for tourists.” Nightmare smiled again, back in control. He lifted himself up out of the mud with his tentacles, stuffing his hands in his gooey pockets and waving his other appendages menacingly. He made quite the figure, looming over Blue and looking all the world like the harbinger of death. “Come and get me, you Sans reject.”

Sans chuckled.

Blue yelled a wordless cry, his boots slipping and skidding in the awful mud that was only getting worse by the moment. He landed blows on Nightmare’s tentacles but they were more resilient than the rest of him, absorbing each punch and sticking to Blue’s gloves. With a laugh, Nightmare descended. The two skeletons became one in a ball of flying fists and drippy limbs. They were shouting at each other, but through the rain and their furry, they could no longer be understood.

Dream yawned politely behind one gloved hand. “Perhaps I ought to break them up now. They are making quite the… what are they doing?”

The fighting had gone quiet, although the rolling around in the mud seemed to have intensified. Sans squinted at them, trying to make sense of it all. When it finally clicked, he coughed into his fist. “Maybe uh,” he grabbed Dream by the elbow and spun him around to face the other direction. “Maybe we’ll just turn this way for a bit, eh?”

“What? Why? What are they doing?”

A small blush on Sans’ cheeks betrayed his discomfort. He might have teleported them both out of there, but there was also a chance that they would go… back… to fist fighting and him and Dream might really need to split them up. “Just… give them a bit of space.” 

It was slightly easier to ignore the grunting in the pouring rain. Sans hoped it didn’t let up too soon.

How or when the energy changed between the two, neither would be able to say later. But forceful blows somehow became forceful caresses, growls became breathless gasps. With shaking hands they tugged at each other’s clothing, ignoring the sticky glop of the dark skeleton as much as they ignored the mud, or the others trying discreetly not to watch. Neither cared.

Nightmare’s tentacles found openings in Blue’s clothing, through the neck of his tunic, in the arms, up his shorts. Curling and expanding and stressing the seams until they finally began to pop, scraps of cloth falling away beneath them to be then buried by their bodies. Nightmare’s own clothes seemed to simply melt away from him until the contrast was palpable, a white and a black skeleton passionately tumbling around in the brown mud.

It would seem to on lookers that both were trying to pin the other to the ground. Telltale blue glows basically surrounded them both, although Nightmare’s light was considerably muted. Neither seemed concerned with the massive erections between them. Blue’s cock throbbed almost painfully, so eager was he to continue. Nightmare’s own considerable penis flexed and twisted, another tentacle in a mass of tentacles, acting practically independently of his body. It lashed out, trying to snag Blue in its strange grip.

Blue somehow finally managed to pin Nightmare by his shoulders. The momentary astonishment allowed Blue to shove himself home. There was a flash of lightening, and thunder rumbled overhead as both of them shuddered, shocked. Nightmare had gone stiff, his one bright eye gone wide.

Breathless panting filled the air and Blue smiled. “Nyeh he-heh! I… I got you!” Although he didn’t seem entirely sure of what he had.

Nightmare wasn’t moving, his tentacles were frozen in midair, surrounding them like a spider clutching prey. His cock had no such issues however and it began to move again, stretching and curling around and down. Blue could only stare, watching Nightmare as he slowly smiled, and feeling as… as that tentacle found his own anus, teasing him a moment before leisurely, almost tenderly, inserting. 

Blue closed his eyes, he was shaking on top of Nightmare. The dark tentacles closed in, wrapped about the two of them even closer until they were encased, in a cocoon of black with the occasional flash of white and blue peeking through the cracks.

The mass of skeleton began to undulate.

Sans couldn’t help but turn his head to see how they were doing, only to blush fiercely and try to engage Dream in some awkward conversation. 

Both Nightmare and Blue thrust gently at each other, back and forth in a strange dance. Rain poured down over them and they sank a little deeper into the mud. Blue couldn’t help but grunt as Nightmare filled him, the dual sensations of being inside of someone and having someone inside of him driving him a little crazy. His tongue lolled out of his mouth, he couldn’t hold onto it anymore. Nightmare’s smile only widened more. His dark arms reached out and drew Blue closer to him until their chests clunked together, long strings of goop sticking to every inch of those white bones.

Nightmare, a strange but comfortable fog filling his head, conjured his own tongue, wrapping it around Blue’s and tugging playfully. They were now completely wrapped up in each other, the ball of skeleton growing tighter and tighter. Neither stopped moving though, if anything their movements became more intense, more erratic.

Blue gave in completely then, forgetting the insults and the injuries, his mind focusing in on the movement, on the pleasure. His whole body tingled and tickled where Nightmare’s form stuck to him and tugged at him. With those ever moving tentacles hugging him, caressing and gyrating over his bones, there seemed to be some sort of sensation over his entire frame. The stimulation was too much, his mind couldn’t cope, nothing else seemed to exist. 

Nightmare, enjoying this strange mixture of them both being in charge, felt a change come over Blue. His breathing became very shallow, his bones twitched and his thrusting came in spams. Backing off with the cocoon a little, Nightmare instead wrapped one thick tentacle around Blue’s spine, effectively taking control of the skeleton’s movements. 

This seemed to bring Blue back again and the lighter skeleton smiled, closing his eyes, and seemed to enjoy himself. Nightmare wasn’t sure exactly why but, well, he liked that. The more he watched Blue in this happy state, grunting with pleasure, mumbling under his breath for Nightmare to move faster, the closer he came to release.

“Blue… hey uh… I’m gonna…”

“D-do it.” Blue muttered, a sleepy, happy grin on his face. 

Thrust “I’m gonna…” thrust “I’m gonna…”

His whole body tensed and convulsed, his grip tightened around Blue, testing his limits. His cock practically bulged with his load and Blue would swear later that he could feel it, even as he felt Nightmare cum hot inside of him, filling what little ecto flesh he had managed to conjure there.

There was some triumph in Blue’s orgasm that managed to outlast Nightmare by mere seconds. Nightmare’s tentacles spasmed and shook, then went limp.

The two breathed heavily together, neither too keen on moving any time soon, both of them dripping with a myriad of fluids that the rain slowly washed away.

Blue sneezed.

Sans, suddenly beside him, tucked a shoulder under the taller skeleton’s arm and helped him up on shaking legs. “Hey buddy, how about I take you home and get you some hot chocolate?”

Blue blinked sleepily, his knees knocking together. “Hmmm? Yeah… o-okay.”

Sans shook his head at the scattering of Blue’s torn clothes, they were ruined. Blue was much taller than he was and would probably look ridiculous in anything he owned… haha but what choice did he have at this point?

“Hey, Dream? I’m gonna take Blue home. He looks… out of commission for a little while.”

“Yes, certainly.” Dream nodded as he watched Sans teleport himself and Blue away, leaving him there with the mass of tentacles and teeth. Nightmare rested his head in his hands, smiling widely up at the sky as his clothing slowly reformed.

“You’re such a pig, you know that?”

Nightmare just shrugged. “I thought it went quite well, myself.”

“Are you telling me you set out to do this from the start? All these trips we’ve taken through here just so you can have a go at Blue?”

He shrugged again, but his happy expression said it all.

“Ugh.” Dream tossed his hands in the air. “Clean yourself up, we’re supposed to be long gone by now.” He walked off, leaving Nightmare to catch up on his own.


End file.
